Cd45 deficiency is a rare genetic immune disorder that weakens the body’s ability to fight infections. People with Cd45 deficiency often have frequent or severe infections and may not respond well to routine vaccines. It usually starts in infancy or early childhood and tends to be lifelong. Treatment focuses on preventing and treating infections, and some may benefit from stem cell transplant. The outlook varies with severity and access to care, but early evaluation and consistent follow-up can improve outcomes.
Overview
Cd45 deficiencySymptoms
Early signs of CD45 deficiency often appear in infancy: frequent, severe infections (chest, ear, skin), slow weight gain, and persistent thrush or diarrhea. Many have poor responses to vaccines and prolonged fevers. Doctors may notice very low lymphocyte counts.
Outlook and prognosis
Many living with CD45 deficiency face frequent, hard‑to-clear infections early in life, and some develop serious immune complications. With prompt diagnosis, protective antibiotics, and timely stem cell transplant when appropriate, outcomes have improved markedly. Ongoing specialist care helps reduce infections and supports healthy growth.
Causes and risk factors
Cd45 deficiency results from harmful changes in the PTPRC gene, usually inherited in an autosomal recessive pattern or rarely from a new mutation. Risk rises with family history or parental relatedness. Crowded living, infections, and live vaccines can worsen outcomes.
Genetic influences
Genetics is central in Cd45 deficiency, which results from inherited changes in the PTPRC gene. Most cases follow autosomal recessive inheritance, so both parents typically carry a silent variant. Different variants can change severity, infection risk, vaccine responses, and transplant outcomes.
Diagnosis
Doctors suspect Cd45 deficiency from clinical features like early, severe infections. Diagnosis is confirmed by blood tests showing absent CD45 on white blood cells and genetic tests, often termed the genetic diagnosis of Cd45 deficiency.
Treatment and drugs
Treatment for Cd45 deficiency focuses on preventing infections, supporting the immune system, and addressing complications early. Care may include prompt antibiotics, antiviral or antifungal medicines, immunoglobulin replacement, and vaccines tailored with specialist guidance. In select cases, stem cell transplantation offers a potential long‑term solution.
Symptoms
Cd45 deficiency affects the immune system, so the most noticeable signs are frequent, hard-to-treat infections and trouble gaining weight. In medical terms, this is a severe combined immunodeficiency; in everyday life, it shows up as infections that are more serious, last longer, or keep coming back. Parents often ask about early features of Cd45 deficiency, which usually show up in the first months of life.
Early on, this might look like back-to-back ear or sinus infections that take longer to clear. In Cd45 deficiency, infections tend to be harder to treat and may return soon after finishing antibiotics.
Pneumonia or deep chest infections can cause persistent cough, fast breathing, or wheeze. Recovery often takes longer than expected and may need hospital care.
White patches in the mouth or a stubborn diaper rash can keep coming back. These fungal infections are more common when T cells do not work well.
Common viruses like RSV, influenza, or chickenpox can be unusually heavy or prolonged. Some people with Cd45 deficiency may have complications that need antiviral medicines or hospitalization.
How people usually first notice Cd45 deficiency?
Many families don’t notice anything at birth, but the first signs of CD45 deficiency often appear in the first months of life when a baby has unusually frequent, severe, or hard‑to-clear infections, sometimes with poor weight gain and prolonged fevers. Doctors may first suspect it after blood tests show very low or missing types of white blood cells that coordinate the immune response, or when routine vaccines don’t trigger the expected protection. In some cases, newborn screening for severe immune problems or an evaluation after a serious early infection is how CD45 deficiency is first noticed.
Types of Cd45 deficiency
CD45 deficiency is a rare genetic condition affecting immune cell signaling, usually caused by changes in the PTPRC gene that encodes the CD45 protein on white blood cells. Different variants of CD45 deficiency are recognized based on which CD45 isoforms are absent or reduced and how much signaling is affected, which can shift severity from frequent infections to combined immune problems. Symptoms don’t always look the same for everyone. Understanding the main variants of CD45 deficiency can help people and clinicians talk clearly about the types of CD45 deficiency they might encounter.
Classic immunodeficiency
Marked loss of CD45 across key immune cells leads to serious, early, and recurrent infections. Babies and children may have trouble clearing common viruses and bacteria and may need hospital care. Some also show features of combined immune deficiency.
Isoform-selective variant
Certain CD45 isoforms are reduced while others remain, changing how T cells and B cells activate. Infections may be milder or appear later, sometimes after routine vaccines or common viral illnesses. Doctors sometimes classify symptoms as mild-to-moderate versus severe based on infection pattern and lab tests.
Hypomorphic mutation
Partially working CD45 results in lower-than-normal signaling rather than a complete loss. People may have recurrent ear, sinus, or chest infections but still grow and develop fairly well between illnesses. The balance of symptoms can shift over time.
Regulatory signaling defect
Qualitative changes in CD45 function disrupt fine-tuning of immune responses more than overall cell counts. This can look like frequent viral infections along with autoimmunity, such as low platelets or thyroid issues. Loved ones may recognize certain types sooner than the person experiencing them.
What genetics can tell you about symptoms
Certain PTPRC (CD45) gene variants can severely lower CD45 on immune cells, leading to frequent, hard‑to‑clear infections, slow wound healing, chronic diarrhea, and poor vaccine responses. Some variants change CD45 “isoforms,” which can trigger autoimmune problems like rashes, joint pain, or low blood counts.
Causes and risk factors
Cd45 deficiency usually results from changes in the PTPRC gene present from birth. Most cases are inherited in an autosomal recessive way, but a new mutation can also occur. A main risk factor for Cd45 deficiency is when both parents carry the same gene change, especially if they are related by blood. Infections, nutrition, and other health issues do not cause Cd45 deficiency, but they can affect how severe the immune problems become. Genetic testing can sometimes clarify your personal risk.
Environmental and biological risk factors
Understanding what can raise the chance of a condition can help during family planning or prenatal conversations. Cd45 deficiency is present from birth, and its likelihood is shaped mostly by factors at conception rather than day-to-day exposures. Awareness of both biological and environmental influences helps you feel prepared. These factors are different from early symptoms of Cd45 deficiency, which describe how the condition appears after birth.
There are currently no specific environmental links clearly tied to higher risk of Cd45 deficiency. Large studies have not identified consistent outside triggers. Research continues to watch for any patterns.
The main drivers of risk arise at the moment the egg and sperm join. These intrinsic events are not known to be altered by everyday environmental conditions.
Older paternal age raises risk for some new-at-conception conditions, but this pattern has not been shown for Cd45 deficiency. Current data do not indicate a meaningful increase in risk with typical aging of fathers. If concerned, ask your clinician how age fits into the broader picture.
High-dose ionizing radiation to a parent before conception can harm reproductive cells. This has not been directly linked to more cases of this condition, but minimizing unnecessary high-dose exposure is advised.
Genetic risk factors
Cd45 deficiency is caused by changes in a single gene, and the risk runs in families. Understanding the genetic causes of Cd45 deficiency can help families plan, test relatives, and discuss options with a genetics team. In some cases, genetic testing can give a clearer picture of your personal risk.
PTPRC gene changes: Changes in both copies of the PTPRC gene stop the CD45 protein from working on white blood cells. This blocks key immune signals and leads to Cd45 deficiency. Most changes prevent the cell from making a functional protein.
Autosomal recessive inheritance: A child is affected only after inheriting two nonworking copies, one from each parent. Carrier parents are usually healthy. Each pregnancy has a 25% chance of Cd45 deficiency.
Carrier status: People with one PTPRC change are carriers and typically have normal immunity. Each child of a carrier has a 50% chance to inherit the variant. Testing can identify carriers in a family.
Parental relatedness: When parents are related by blood, they are more likely to share the same rare PTPRC variant. This raises the chance of an affected child. Genetic counseling can explain personal risk.
Founder variants: In some communities with shared ancestry, a specific PTPRC change may be more common. This can increase the odds that both partners carry the same variant. Carrier screening may be offered in high risk groups.
Family history: Having a sibling or close relative with Cd45 deficiency signals higher inherited risk. Brothers and sisters of an affected child each have a 25% chance to also be affected. Relatives may benefit from carrier testing.
Variant effects: The specific gene change can influence how much CD45 is made. Complete loss often causes severe, early infections, while rare partial loss may look milder or atypical. People with the same risk factor can have very different experiences.
Lifestyle risk factors
Cd45 deficiency is a genetic immunodeficiency; lifestyle habits do not cause it, but they can influence day‑to‑day infection risk, symptom control, and complications. The points below focus on how lifestyle affects Cd45 deficiency by altering exposure to pathogens, supporting immune resilience, and optimizing treatment effectiveness. Choose changes with your clinical team so they align with your specific immune status and therapies.
Consistent handwashing, mask use in high-risk settings, and avoiding close contact with sick individuals can meaningfully cut respiratory and gastrointestinal infections. Quick isolation and testing when symptoms start may reduce severity and spread.
Regular meals with enough protein, calories, and micronutrients (like vitamin D and zinc) support mucosal barriers and wound healing, which may lower infection complications. Poor intake or restrictive diets can worsen fatigue and delay recovery from infections.
Taking prophylactic antibiotics, antivirals, antifungals, or immunoglobulin on schedule lowers breakthrough infections and hospitalizations. Skipping or delaying doses increases the chance of severe infection and resistance.
Short or irregular sleep disrupts immune signaling and is linked with higher infection susceptibility. A steady 7–9 hour sleep window may improve vaccine responses to inactivated vaccines and reduce illness duration.
Risk prevention
Cd45 deficiency is a rare, inherited immune disorder, so you can’t prevent the condition itself, but you can lower the risk of infections and complications. Prevention focuses on everyday infection control, tailored vaccines for the household, and medical steps that boost protection. Prevention works best when combined with regular check-ups. Planning ahead with an immunology team helps many families stay a step ahead of infections and hospital visits.
Wash hands often and use alcohol gel when soap isn’t available. Avoid close contact with people who are ill and consider masks during community outbreaks.
Make sure family and close contacts are fully vaccinated to create a protective “cocoon.” Annual flu and updated COVID-19 shots for household members lower exposure for people with Cd45 deficiency.
People with Cd45 deficiency should avoid live vaccines such as MMR, varicella, and certain nasal flu sprays. Ask your specialist to map out a safe vaccine plan.
Antibody replacement (IVIG or SCIG) can reduce how often and how severely infections happen. Your immunology team will decide dose and schedule.
Transmission
Cd45 deficiency is a genetic condition present from birth and is not contagious. Most cases follow autosomal recessive inheritance: each parent carries one silent, nonworking copy of the CD45 gene, and when two carriers have a child, there is a 25% (1 in 4) chance the child will have Cd45 deficiency, a 50% (1 in 2) chance the child will be a carrier, and a 25% chance of inheriting two working copies. Occasionally, Cd45 deficiency can arise from a new (de novo) gene change, so parents may test negative as carriers. Because genetic transmission of Cd45 deficiency runs through families, options like carrier screening and prenatal or newborn testing can clarify how Cd45 deficiency is inherited and the chances for future pregnancies.
When to test your genes
Test your genes if you have repeated severe infections, unusually low white blood cells, or a close relative with confirmed CD45 deficiency. Consider testing before stem cell transplant or biologic therapy, since results can change dosing, donor choice, and infection prevention. Newborns or children with concerning immune screens also warrant prompt genetic testing.
Diagnosis
People with Cd45 deficiency often face frequent or unusually severe infections, sometimes starting in infancy, which can make ordinary colds linger and routine vaccines less protective. Getting a diagnosis is often a turning point toward answers and support. Doctors rely on recognizable patterns in the immune system and confirm them with specific tests. The diagnosis of Cd45 deficiency is typically made by finding missing or very low CD45 on white blood cells and confirming the genetic change that causes it.
Doctors ask about infections that are frequent, severe, or hard to treat, and look for signs like poor weight gain or swollen lymph nodes. This clinical picture helps raise suspicion for an immune system disorder.
A complete blood count checks the number of white blood cells, red cells, and platelets. Results can suggest an immune problem but usually are not enough to confirm Cd45 deficiency on their own.
A test called flow cytometry measures CD45 on white blood cells and maps T cells, B cells, and NK cells. Very low or absent CD45 expression strongly supports the diagnosis of Cd45 deficiency.
Labs may test how T cells respond to stimulation to see if they can activate and multiply. Poor responses add evidence that the immune signaling pathway is not working properly.
Stages of Cd45 deficiency
Cd45 deficiency does not have defined progression stages. Early symptoms of Cd45 deficiency often involve frequent or severe infections and poor weight gain, and the pattern varies by how strongly the immune system is affected rather than moving through set phases. Doctors usually start with a conversation about recent infections and growth, then run blood tests to check white cells and how they work, review newborn screening results, and may add flow cytometry to look for the CD45 marker. Genetic testing can confirm a change in the CD45 (PTPRC) gene and helps plan care and follow-up.
Outlook and prognosis
Many people ask, “What does this mean for my future?”, especially after learning about Cd45 deficiency. Day to day, people with Cd45 deficiency may deal with frequent infections, slow recovery from common colds, or hospital visits for pneumonia or bloodstream infections. The outlook is not the same for everyone, but early symptoms of Cd45 deficiency in infancy—such as recurrent ear infections, poor weight gain, or thrush that keeps coming back—usually signal a more severe course without treatment. In medical terms, the long-term outlook is often shaped by both genetics and lifestyle, including which CD45 gene change is present, exposure to infections, and access to prompt medical care.
Looking at the long-term picture can be helpful. Without definitive therapy, serious infections and complications like chronic lung damage can shorten life expectancy, and some children may face life‑threatening illness early. With timely antibiotics, infection prevention, and immune‑supportive treatments, many people maintain better health while planning for curative options. The most effective long‑term treatment is often a stem cell transplant, which can restore immune function and, in successful cases, bring survival closer to that of peers.
Everyone’s journey looks a little different. Outcomes improve when problems are caught early, vaccinations are tailored, and care is coordinated at an immune‑disorders center. Support from friends and family can help with home infection‑prevention routines, clinic visits, and the stress that comes with a rare diagnosis. Talk with your doctor about what your personal outlook might look like, including transplant candidacy, expected infection risks, and steps you can take now to stay as healthy as possible.
Long-term effects
Cd45 deficiency can shape health over years because the immune system struggles to clear infections and control inflammation. Long-term effects vary widely, and some remain mild while others become more serious. Outlook often depends on how early the condition is recognized and whether complications are prevented. Over time, issues can involve the lungs, blood, gut, skin, and growth.
Repeated bacterial, viral, and fungal infections can continue into childhood and adulthood. These infections may be more severe or longer-lasting than usual.
Ongoing chest infections can scar the airways and lead to bronchiectasis. This can cause daily cough, mucus, and breathlessness over time.
The immune system may attack the body’s own tissues, especially blood cells. People with Cd45 deficiency can develop autoimmune anemia, low platelets, or thyroid issues.
Some develop enlarged lymph nodes or spleen due to immune dysregulation. Over many years, a small number may face an increased risk of lymphoma.
How is it to live with Cd45 deficiency?
Living with CD45 deficiency often means frequent, sometimes severe infections starting in infancy or early childhood, along with fatigue from the body working overtime to fight germs. Daily life can revolve around infection prevention—hand hygiene, avoiding crowded spaces during outbreaks, staying current with vaccines that are safe for weakened immune systems, and keeping close follow-up with immunology specialists. Families and close contacts may adjust routines to reduce exposure, learn to spot early signs of infection, and support treatment plans such as antibiotics, immunoglobulin infusions, or, in some cases, preparation for stem cell transplant. Many find a new rhythm over time, building safety nets at school, work, and home so life feels more predictable and connected rather than limited.
Treatment and drugs
Treatment for Cd45 deficiency focuses on restoring immune function, preventing infections, and managing complications. For many people, treatment begins with small daily steps like strict infection prevention, prompt antibiotics or antivirals when sick, and up-to-date vaccines using non-live formulations. The only curative option is a stem cell (bone marrow) transplant, which replaces the faulty immune system; doctors may use conditioning chemotherapy beforehand and supportive medicines such as antifungals and immunoglobulin infusions while the new cells engraft. Not every treatment works the same way for every person, so timing of transplant, donor choice, and the need for ongoing immunoglobulin replacement are tailored to each individual’s health and infection history. Ask your doctor about the best starting point for you, including referral to a transplant center experienced in rare immune deficiencies.
Non-drug treatment
Living with Cd45 deficiency often means focusing on everyday ways to lower infection risk and protect overall health. Non-drug treatments range from careful hygiene and home strategies to procedures like stem cell transplant, plus supportive therapies that keep nutrition, lungs, and mood on track. Non-drug treatments often lay the foundation for staying well between medical visits. Your care team can tailor these steps based on age, early symptoms of Cd45 deficiency, and family needs.
A hematopoietic stem cell transplant can rebuild the immune system. It’s a procedure rather than a medicine and may offer a long-term solution in severe cases. Timing and donor matching are key.
Handwashing, masks during outbreaks, and avoiding sick contacts reduce exposure. Safe food handling and clean home surfaces further limit germs. These habits are important during high-risk seasons.
Family and close contacts staying up to date on vaccines helps protect the person with Cd45 deficiency. This “cocooning” lowers the chance of bringing infections home. Live vaccines for the patient may be avoided—ask your care team.
A written plan helps you act quickly if fever, cough, or new rashes appear. Keep emergency numbers handy and know which clinic or hospital to contact. Early evaluation can prevent complications.
Your genes may have an impact on how drugs work for you
Medicines for people with CD45 deficiency can work differently because CD45 helps immune cells receive and send signals, which affects how drugs that boost, calm, or direct immunity perform. Genetic differences in CD45 and related pathways may change dose needs, benefits, and side‑effects.
Pharmacological treatments
Medicines for Cd45 deficiency aim to prevent and control infections and support the immune system while planning for curative options like a stem cell transplant. They don’t fix the genetic cause, but they can lower the risk of serious illness once early symptoms of Cd45 deficiency show up. Alongside drug therapy, infection control and timely stem cell transplant remain important. Doses and timing vary by age, weight (kg/lb), kidney and liver function, and local infection risks.
Intravenous (IVIG) or subcutaneous (SCIG) immune globulin replaces missing antibodies to help prevent sinus, lung, and bloodstream infections. Infusions are given regularly (for example, IVIG every 3–4 weeks or SCIG weekly), with dose adjusted to maintain protective IgG levels. Common effects include headache or infusion-site reactions, which are usually manageable.
Trimethoprim–sulfamethoxazole (TMP–SMX) is used to prevent Pneumocystis jirovecii pneumonia, a serious lung infection. It may be taken daily or three times a week, with alternatives like atovaquone or dapsone if there’s a sulfa allergy (G6PD testing needed for dapsone). Staying on schedule is key to protection.
Fluconazole or itraconazole can reduce the risk of Candida and some mold infections, especially during high-risk periods. Doctors monitor for drug interactions and check liver enzymes, since azoles can affect other medicines. Dosing depends on age and risk level.
Acyclovir or valacyclovir may be used to prevent or suppress herpesvirus infections like HSV. Kidney function guides dosing, and good hydration helps reduce side effects. If exposure risks change, the plan can be adjusted.
Genetic influences
Most cases trace back to inherited changes in the CD45 gene, which helps white blood cells communicate and turn on immune responses. Cd45 deficiency is usually passed in an autosomal recessive pattern—when both parents carry one changed copy, each child has a 25% chance to be affected, a 50% chance to be a carrier, and a 25% chance to inherit neither change. A “carrier” means you hold the gene change but may not show symptoms. Because carriers typically feel well, Cd45 deficiency may not be obvious in a family until a child has serious or repeated infections. Genetic testing for Cd45 deficiency can look for changes in the CD45 gene to confirm the cause, guide care, and help assess risks for siblings and future pregnancies. Severity can differ between individuals, even within the same family, because other genes and life factors can influence how strongly the condition shows up.
Is Cd45 deficiency genetic?
Genetics is central in Cd45 deficiency, which results from inherited changes in the PTPRC gene. Most cases follow autosomal recessive inheritance, so both parents typically carry a silent variant. Different variants can change severity, infection risk, vaccine responses, and transplant outcomes.
Pharmacogenetics—how genetics influence drug effects
In CD45 deficiency, care often includes infection prevention and an early stem cell transplant; some of the medicines used along the way are chosen and dosed with your genes in mind, sometimes using pharmacogenetic testing. Differences in drug‑handling genes can change blood levels of common transplant and infection medicines — for example, people who make little of the CYP3A5 enzyme usually need lower tacrolimus doses, while CYP2C19 differences can make voriconazole levels too low or too high. Genetic testing can sometimes identify how your body processes medicines used around a stem cell transplant, such as tacrolimus or voriconazole. If thiopurines like azathioprine or mercaptopurine are ever considered, checking TPMT or NUDT15 first can reduce the risk of severe drops in white blood cells. Before using dapsone for infection prevention, screening for G6PD deficiency helps avoid dangerous anemia. These results don’t change the need for transplant in CD45 deficiency, but they can help your team pick safer starting doses, cut down on side effects, and support close blood‑level monitoring when needed.
Interactions with other conditions
Living with Cd45 deficiency often means frequent or severe infections, so any illness that targets the lungs, gut, or blood can hit harder and last longer. Doctors call it a “comorbidity” when two conditions occur together, and in this setting, chronic respiratory diseases like asthma or bronchiectasis may worsen because repeated infections inflame and scar the airways. Certain viruses, including cytomegalovirus or Epstein–Barr virus, can cause unusually serious illness in people with Cd45 deficiency, and live-attenuated vaccines may trigger disease rather than protect, so they’re generally avoided. Autoimmune problems can also overlap, and when they do, treatments that suppress the immune system may further raise infection risk, so plans need careful balancing. Understanding early symptoms of Cd45 deficiency alongside signs of infection can help you and your care team act quickly and prevent complications. Close, coordinated care becomes especially important if cancer, chronic lung disease, or gastrointestinal disorders are also present, since antibiotic prophylaxis, immunoglobulin therapy, and timing of vaccines or antivirals may need to be adjusted.
How genes can cause diseases
Humans have more than 20,000 genes, each carrying out one or a few specific functions in the body. One gene instructs the body to digest lactose from milk, another tells the body how to build strong bones and another prevents the body's cells from beginning to multiply uncontrollably and developing into cancer. As all of these genes combined are the building instructions for our body, a defect in one of these genes can have severe health consequences.
Through decades of genetic research, we know the genetic code of any healthy/functional human gene. We have also identified that in certain positions on a gene, some individuals may have a different genetic letter from the one you have. We call these hotspots "Genetic Variations" or "Variants" in short. In many cases, studies have been able to show that having the genetic letter "G" in the position makes you healthy, but having the letter "A" in the same position disrupts the gene function and causes a disease. Genopedia allows you to view these variants in genes and summarizes all that we know from scientific research, which genetic letters (Genotype) have good or bad consequences on your health or on your traits.
History
Throughout history, people have described children who seemed healthy at birth but then faced frequent, serious infections that were hard to treat. Families remembered infants who didn’t respond to routine vaccines, had repeated chest infections, or struggled to gain weight despite careful care. Looking back, many of these patterns match what we now recognize as CD45 deficiency, a rare immune disorder.
First described in the medical literature as a form of severe combined immunodeficiency (SCID), CD45 deficiency was initially grouped with other conditions where both T and B cells don’t work properly. Early reports focused on the recurring infections and poor vaccine responses, because doctors didn’t yet know the exact molecular cause. As testing improved in the late 20th century, researchers identified CD45 (also called PTPRC), a key protein on white blood cells that helps them activate and communicate. When the CD45 gene is changed in certain ways, immune cells can be present but unable to “switch on,” leaving people vulnerable to infection.
From early theories to modern research, the story of CD45 deficiency follows the broader progress of immunology. At first, careful clinical observation linked symptoms like persistent thrush, chronic diarrhea, and severe respiratory infections to deeper immune problems. Then, immune profiling showed that T cells might be present in normal or near‑normal numbers, yet function poorly. Genetic studies later confirmed that specific variants in the CD45 gene cause these signaling problems, explaining why some children had SCID-like illness even when standard cell counts looked less alarming.
Awareness grew that CD45 deficiency can vary in severity. Some infants became very ill in the first months of life, while others had later or somewhat milder courses, depending on how the gene change affected CD45’s function. This variability helped clinicians refine the diagnosis and distinguish CD45 deficiency from other primary immunodeficiencies. Importantly, newborn screening programs for SCID, which spread in recent decades, made it easier to detect serious T‑cell problems early, prompting genetic confirmation and timely treatment.
Advances in genetics also influenced care. Once the specific cause was known, bone marrow transplantation emerged as a path to rebuild the immune system, and supportive measures—such as infection prevention, immunoglobulin replacement, and careful vaccine planning—became more targeted. Not every early description was complete, yet together they built the foundation of today’s knowledge. Today, CD45 deficiency is recognized as a distinct, inherited immune signaling disorder, rare but important to identify early, because prompt diagnosis can change the course of a child’s health.